Electric Fluid Heater

The present application is a continuation of U.S. patent application Ser. No. 18/695,102, with a filing or 371(c) date of Mar. 25, 2024, which is a U.S. National Stage Application of PCT International Application No. PCT/GB2022/052711 filed Oct. 25, 2022 and published on May 4, 2023 as WO 2023/073356 A1, which claims priority from United Kingdom patent application 2115477.8 filed on Oct. 27, 2021, all of which are incorporated by reference in their entirety.

This invention relates to electric heaters for fluid heating systems. In particular, but not exclusively, the invention relates to electric boilers for wet heating systems or electric furnaces for air heating systems, both of which can supply heated fluid for heating spaces (such as via radiators) or heated tap water or both.

Gas boilers can provide wet heating solutions for hot water and heating needs. For example, a domestic gas boiler will often supply hot water for heating radiators within a heating system and also provide on-demand hot water to taps (e.g. for drinking, cleaning, washing). The two supplies (heating and tap) are kept separate since the heating water can become dirty as it passes through a radiator circuit, whereas tap water must be clean. Combination (“combi”) boilers are popular as they provide all of this functionality within a sealed, high pressure environment within a single boiler housing with a relatively small physical footprint. Other types of boilers having separate tanks or cylinders are also used.

Gas boilers burn fossil fuel. As a result, electric boilers are now emerging as an environmentally friendly alternative. An electric boiler will pass the water via an electric heating element.

An electric combi boiler uses similar technology to an electric kettle. The electric boiler is connected to the mains electricity supply and is supplied with cold water from the mains. When hot water is requested (e.g. when a hot water tap is opened or the heating is switched on), the heating element inside the electric boiler heats up and passes this heat to the cold water. The heated water is then pumped to the tap or radiator where it is needed.

Storage electric boilers include a hot water tank (either an internal tank within the unit or an external tank). This enables heating and storage of water at times when energy costs are lower (e.g. overnight) for subsequent use at times when energy costs are higher (e.g. the next day). Such systems take up more space.

Along the same theme, but offering some of the advantages of a combi boiler, a combined primary storage unit (CPSU) has the central heating boiler and hot water cylinder combined in one big housing—this provides large amounts of hot water whenever required. However, a lot of space is required to house this system.

All of these electric boiler systems use heating elements powered by the AC (alternating current) mains supply.

The inventors have realised that a better electric boiler can be produced and have created the claimed solution.

According to a first aspect of the present invention, there is provided a fluid heater A partially or wholly electric fluid heater arranged to heat fluid in a first circuit, the fluid comprising heating fluid or tap water, wherein the heater comprises a heater housing arranged to house a first heater vessel containing a first electric heating element arranged to heat fluid in the first circuit; and a DC power supply arranged to at least partially power the first heating element, the DC power supply having a capacity of at least 1 kWh, the heater further comprising a heat shield located between the DC power supply and the first heater vessel.

Advantageously, a fully electric or hybrid electric fluid heater that can rely solely on a DC power supply (i.e. need not rely on AC input) is provided. This type of heater is eco-friendly relative to pure gas burning (or other combustible fossil fuel burning) boilers.

Optional features of the invention are as claimed in the dependent claims—various advantages are thereby provided as discussed in the detailed description. These optional features add efficiency and intelligence to the inventive heater setup. Any of these optional features may be combined with any other of the optional features as will be appreciated by those skilled in this art.

The exemplary embodiments described in the detailed description and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the scope of the invention. Various embodiments are described. The specific embodiments are not intended as an exhaustive description or as a limitation to the broader discussed and claimed aspects. Features described in conjunction with a particular embodiment are not necessarily limited to that embodiment and can be incorporated into any other embodiment(s). Protection afforded by any applicable doctrine of equivalents is retained to its fullest extent.

Terms such as up, down, top, bottom, left, right, inner, outer, vertical, upstanding etc. have been used to simply and clearly describe the invention. These terms are not to be interpreted in a manner that would be limiting. The person skilled in the art will envisage other suitable embodiments within the scope of the invention.

Referring to, there is shown a water heater(also referred to as a boiler herein) used to heat water for use in a standard fluid circuit, such as a radiator heating water circuit. Various aspects of the boiler and boiler system will be described in detail with reference to non-limiting examples. Other details will be apparent to the skilled person. In particular, aspects (including undescribed aspects) of known boiler systems can be incorporated and used with this invention by the skilled person.

Generally, the boiler may be a tank-type boiler (known also as a system boiler), or a combi boiler, or any other known boiler type, or a furnace heater, such as a furnace air heater. The skilled person will be able to adapt the described embodiments to boiler types other than those described. As is known, these boiler types can be used to supply heating water (e.g. to a radiator circuit) or potable water (e.g. to a circuit of taps) or both. In other examples, instead of heating radiator water, there may be another type of heating fluid flowing through the heating system, e.g. another liquid, another gas (e.g. air) or oil or any combination thereof.

Such fluid circuits are well known in the field. The, any or each fluid circuit may be a substantially sealed fluid circuit in use and optionally may be pressurised. In a potable water circuit, pressure from the mains or gravity fed source drives water such that when a faucet/tap is opened, water flows out of tap in normal use. Typically, a radiator circuit is substantially sealed in normal use. Bleed points or pressure release points may be provided at convenient locations to allow inspection or pressure release or fluid release for maintenance and repair. It is known to use expansion tanks or expansion vessels (which are small tanks used to protect closed (not open to atmospheric pressure) fluid heating systems and domestic hot water systems from excessive pressure). Typically, expansion tanks are partially filled with air, whose compressibility dampens shock caused by water hammer and absorbs excess water pressure caused by thermal expansion. In an air heater, the fluid circuit usually comprises at least one vent through which heated air exits to the space to be heated. In such circuits, the air within the circuit is not sealed from the environment—it is typically at atmospheric or ambient pressure. In some such systems, air is drawn into the furnace during normal operation, heated and then blown around the heated network.

In this example, the water heateris a system boiler and comprises a boiler housingto house its components. Often the boiler of this invention will be required to fit in a small space. In many examples, this invention includes features that make the boiler compact to allow the boiler to fit within the same housing or space footprint as a typical known boiler, even though the inventive boiler comprises a new component (as will be described in more detail below).

The boileris arranged to heat water in a first circuit, wherein the first circuit is a heating water circuit. The heating water circuit comprises multiple components, including standard domestic radiators (not shown) in addition to the boiler. Water is used as the heating fluid within the first circuit in this example; other known heating fluids can be used in other examples.

Relatively cold water from the first circuit enters the boilervia a cold water input pipe, is heated and then relatively hot water exits the boilerto the first circuit via a hot water output pipe.

The boilercomprises an electric boiler vessel, which is located within the housingbetween the inputpipe and outputpipe. The electric boiler vesselis a closed, sealed vessel containing a first electric heating elementarranged to heat water passing through the vessel.

As per this invention, the first electric heating elementis powered by DC power supply, in this example a DC power supply in the form of a battery pack, which is also located within the housing. In this example, the boiler is a fully electric boiler. i.e. the heat source is all electric. In other examples, the boiler may be part electric, e.g. part electric and part gas, or part electric and part other combustible fuel-a suitable combustible fuel may be a combustible fluid such as natural gas, hydrogen gas, or propane gas or methane gas, or ethane gas, or butane gas, or a suitable combustible oil or a combustible solid or mulch, such as woodchip or wood pellet, or any combination thereof. In this way, some of the heating power is provided by the electric DC component and some of it is provided by more traditional burnt fuel. This can help to add redundancy within the system, or can be used to operate efficiently in an environment where one or other power source is scarce. In this invention, the DC power source is large enough to supply or nearly all of the power output of a typical boiler if required.

In this example, the DC power supply has a capacity of 1 kWh.

In another example, for a small gas-electric hybrid boiler system setup, the battery capacity may be about 1 kWh—this might be useful in a small dwelling, such as a small apartment or it may be useful in a larger dwelling as a boost to the usual hot water supply.

In another example, for a larger gas-electric hybrid boiler system setup, the battery capacity may be about 3 to 5 kWh—this might be useful in a larger dwelling.

In another example, for a fully electric boiler system setup, the battery capacity may be about 5 kWh or above. In most cases, if the capacity is 15 kWh to 20 kWh, then water heating needs can be almost solely met by the boiler using DC electric power. E.g., for a fully electric boiler in a small apartment, the battery capacity may be about 10 kWh, in a medium house may be about 15 to 20 kWh, and in a large house may be about 25 to 30 kWh.

In some examples, the battery capacity may be about 90 kWh, e.g. to supply heating fluid and heated potable water to larger buildings.

In this example, the peak power output of the DC power supply is between 10 kW and 20 kW in some examples, and upto 200 kW in some examples. In low peak demand circuits, the peak power output may be 1 kW or 2 kW. Suitable peak power output provisions can be made according to specific circuit requirements and will be apparent to the skilled person. E.g. in one example scenario, a 90 kWh battery might provide 350 kW for 10 minutes.

In this embodiment, the battery packcomprises a stack of batteries in a compact, ordered cell arrangement.

In this example, the 1 kWh DC battery packcomprises one hundred replaceable or rechargeable cylindrical cells, such as standard sized 18650 cells (18 mm diameter and 65 mm length), each having a capacity of about 10 Wh. In this example, the rechargeable cells are arranged in a 10×10 stack for compactness and the entire stack can be removed from the battery packand recharged externally from the housing. In another example, the stack may be a 5×20 stack. Other suitable stack configurations will be apparent depending on the available space for the battery pack. The stack is configured to provide substantially consistent use over time of each cell within the stack in a known manner so that the stack operates effectively as a single unit. In some examples, the DC power source can be charged from renewable heat sources too, such as solar or wind or a heat pump or any other suitable source.

In other embodiments, the DC battery pack can be charged in situ, i.e. without removing any cells from the housing, via a charging connection (not shown).

Charging is carried out in this example by a battery charging mechanism comprising an AC to DC converter in this example, and in examples where the charging is carried out in situ, the boiler further comprises an AC to DC converter located within its housing.

A typical 18650 cell has a voltage of 3.6V. In this example, the cells in the packare arranged in series, i.e. the effective voltage is about 3600V. The pack is well insulated. In other examples, the cells may be arranged differently, e.g. all in series (so that the maximum voltage in any single path is 3.6V) or in parallel paths having a few cells in series, e.g. 10 parallel paths, each having 10 cells (36V) in series.

In some embodiments, cells can be arranged to provide substantially the same voltage as an AC input supply voltage—this makes combining AC and DC easier, and makes charging easier too. E.g. in the UK, a 240V battery pack may be provided. In some examples, a slightly lower DC voltage battery pack may be provided, but still of a value approximately the same as the AC input supply voltage—the skilled reader will be able to determine suitable values.

In some embodiments, instead of a single battery pack, multiple battery packs or stacks within a battery pack are provided.

The boilerhousing also has an AC connectionin order to power small electronic components (these have a relatively low power demand compared to the power required to heat water during normal boiler operation) such as switching circuitry, boiler display screen, boiler user interface, sensors, Wi-Fi, Bluetooth, sub 1 GHz comms etc, led lighting and other standard boiler components. Other such components include: igniter or spark generator; ignition electrode/ionisation electrode; pressure sensor/transmitter (water), also water pressure switch, flow sensor/switch (makes sure that the gas/air mix is flowing correctly before allowing ignition); combustion sensor (thermal switch—sometimes stated separately to temperature sensors by manufacturers); thermostat; thermocouple/PRT; control PCB; multi-media interface; power electronics for powerpacks; pumps (simple electrical or possibly more complex with drive electronics) for water & gas. In some examples, this power may be provided by renewable heat sources too, such as solar or wind or a heat pump or any other suitable source. In some examples, these small electronic components are powered directly from the DC power supply—there is no AC connection to the boiler.

In this example, the boileralso comprises an electric control unit (not shown) arranged to control any one or more of: heating, battery charging, battery discharging, system requirements, switching of the DC power supply. In some examples, the controller is computer controlled and arranged to control the amount of heating supplied to the fluid based on or in response to any one or more control factors, the control factors comprising: amount of heating required; fluid input temperature at an input point in the one or more fluid circuits; fluid output temperature at an output point in the one or more fluid circuits; fluid temperature at any predetermined point in the one or more fluid circuits; amount of heating capacity available from the first heating element; amount of heating capacity available from the combustible fuel burner; instantaneous demand for heating fluid or potable water; forecasted demand for heating fluid or potable water; and flow rate of fluid to be heated.

Furthermore, in some examples, the fluid heater comprises one or more sensors (not shown) arranged to sense information relating to the one or more control factors and to provide said control factor information to the controller. Some of the sensors are located inside the boiler housing (e.g. to measure water temperature or flow rates within the boiler). Some of the sensors are located outside the boiler housing (e.g. to measure water temperature or flow rates at a desired location in the first circuit outside the boiler, such as in a room of a building). The controller acts in response to information from such sensors to instruct heating of the fluid by the fuel burner and electric heating element.

In some examples, the controller may have a memory (not shown) associated therewith (either integrally or separately), the memory being arranged to store information about any one or more aspects of the system, such as historic or sensed information relating to any of the control factors, control factor information, sensed information from any of the sensors, desired output information (e.g. desired room temperature). The controller is able to access information from the memory in a known manner. The controller and memory may be implemented in a standard computerised network and system.

The relatively large battery of this invention produces heat. Other electrical components of the boiler also produce heat. The inventors have realised that a compact, efficient non-standard cooling system is required.

The boilerof this embodiment also comprises a cooling system (not shown). The electronics can get hotter than on a normal boiler because of the large DC battery power involved and extra switching because of intelligent use of a large capacity DC battery, and wanting to use DC-v-AC intelligently (in some embodiments—see below). In some examples, the heater comprises a high-power switching module arranged to efficiently switch high currents such that power can be varied in the same resistant electric heating element and smoothly change fluid temperatures. This is especially important in the potable water circuit. This features allows pulse width modulation within the control circuitry. The high-power switching module may be arranged to switch 30 amps or more.

In examples containing a battery charging mechanism, the inventor further found that heat generation within the battery charging system can be a problem—specifically in an AC-DC converter battery charging system, which allows a voltage to charge the DC battery packs/cells. This type of battery charging mechanism does not exist within any boiler systems or boiler housings yet, and generates heat. A further advantage of some examples of the present invention is therefore to use the cooling system (or to provide a further separate cooling system) as a heat sink to cool the battery charging mechanism too. The battery charging mechanism cooling system can be particularly useful since charging can (and should) also occur when the system is not heating a building or providing hot potable water (e.g., in the middle of the night). The present invention's cooling system allows for running the heating system to leach heat away during charging. The controller may be arranged to run fluid through the fluid heater system to cool the battery charging mechanism even when heated fluid is not required, e.g., the controller may act in response to predicting or being informed or sensing that the battery charging system should be cooled (e.g., via feedback from a temperature sensor located near the battery charger or after the battery has been continuously charging for a threshold minimum time period). This battery charging mechanism cooling feature can be implemented with any of the described embodiments containing a battery charger to create a new embodiment of the invention.

In some examples (e.g., in which flow of the heating fluid/potable water is participating in the cooling), when the heating system is running (e.g., potable water or heated radiator fluid is being demanded), then cooling occurs via flow of the heating fluid/potable water past the controller/battery/battery charger. However, when the heating system is not running, this invention allows for operation of the charger cooling system (whether via flow of the heating fluid/potable water or via its own dedicated coolant within its own dedicated coolant circuit) specifically for the purpose of cooling the battery charger.

In some examples, the cooling system uses some of the water output from the radiators, which arrives at the cold input pipe(typically at about 35-40 deg C.) for cooling the electronics, which are much hotter (ideally, the intention is to keep the electronic components well below 100 deg C.). In some examples, an element of the cooling system comprises locating the first circuit pipework from the inputwithin the boileradjacent or near to the components that require cooling.

The cooling system of this example includes a coolant circuit having a closed coolant pipe system (not shown) through which coolant is pumped. The closed coolant pipe system is configured to encourage heat transfer between the coolant and the boiler's cold water input so as to transfer heat away thereto as well as to encourage heat transfer between the coolant and the battery cells or other components so as to transfer heat away therefrom. This is achieved by routing the pipe system close to any one or more of the boiler components, battery cells and cold water input at appropriate locations.

In the example of, the boiler is configured to be compact. The housing has dimensions 400 cm width by 300 cm depth by 700 cm height and houses the first heater vesselcontaining the first heating element, the DC power supply, and also the cooling system (in this example). In other embodiments, the housing may have dimensions: W390 mm, D270 mm, H600 mm; or W400 mm, D300 mm, H724 mm; or W400 mm, D310 mm, H724 mm; or W440 mm, D365 mm, H780 mm; or W440 mm, D364 mm, H825 mm; or W440 mm, D365 mm, H780 mm; or any other suitable dimensions that will be apparent to the skilled person.

Providing further compactness, the DC power supply is located at a front side, in use, of the housing, substantially fills the space between front and back ends of the housing, and also substantially fills the space between left and right sides of the housing. The boiler has walls on its left and right sides that are relatively inaccessible in use. The front side is relatively accessible and is usually used to access internal components when servicing.

In some examples, the housingcomprises an access door arranged to allow access to internal components of the heater (such as for servicing or repair) and the DC power supply is arranged within or integrally with the access door. This also adds to the overall compactness and also ensures that the DC battery does not need to be further removed or manipulated to access the internal boiler components (e.g. for repair/servicing).

In this example, the boileralso comprises a thermal break or heat shield (not shown) located between the DC power supply and the first heater vessel. The thermal break or heat shield may comprise any one or any combination of: an air gap; a gap filled (partly or fully) by a thermal insulation material; a gap filled (partly or fully) by an infrared-reflective material; a gap filled (partly or fully) by an insulator or low thermal conductivity material.

In some examples, the heat shield may include an associated heat shield cooling mechanism arranged to transfer heat from the heat shield area towards another area in which it is safer to dissipate heat and comprising any one or more of: